Search crews desperately trying to find the missing Titan submersible have detected underwater noises in the area. But it won’t be easy to locate the source of that sound in the ocean.
“It’s not a simple problem,” said Matt Dzieciuch, an expert in ocean acoustics at the Scripps Institution of Oceanography.
The ocean is a “noisy place,” Dzieciuch stressed. There are many other potential sources of sound underwater, including fish, other animals and, of course, man-made instruments, he explained.
The lost submersible could be found at a depth of about 3,800 meters (12,500 feet), near the resting place of the Titanic ocean liner, towards which it was heading on a tourist trip.
On board was the pilot Stockton Rush, CEO of the expedition organizing company, OceanGate. His passengers were a British adventurer, two members of a Pakistani business family and a Titanic expert.
The Coast Guard said search teams heard banging at 30-minute intervals.
But it’s still “speculative” whether those noises are a real sign of life, said Art Trembanis, a marine scientist at the University of Delaware. Even this kind of pattern could come from an underwater instrument making repeating noises.
Usually, an underwater vehicle has a device called a pinger (ultrasonic emitter) that can communicate with the surface and make it easier to locate, Dzieciuch added. However, it remains unclear if the Titan submersible was using one.
One huge challenge is that search personnel don’t know exactly what kind of signal they’re looking for, said Lora Van Uffelen, an ocean engineering researcher at the University of Rhode Island.
“They’re just listening to anything,” he said.
Another challenge for the search crew: Sound waves bend when they travel underwater, due to the way pressure and temperature change at different depths, Dzieciuch said. This can create echo-like effects and make it difficult to locate the source of a particular sound.
“For example, an SOS signal sent by someone from the bottom of the ocean might just sound like a random knock on the ocean surface,” he said. “It’s like yelling into a canyon. You can’t really understand what the person on the other side of the canyon is saying.”
The sounds in the search for the Titan were picked up using devices called sonobuoys, which can be dropped from aircraft to detect noise and avoid interference with sounds from ships, Dzieciuch said. These devices could help triangulate the location of the submarine, but the searchers will need to deploy many buoys for it to work, according to experts.
However, Van Uffelen said that despite the challenges, “the sound is one of the best hopes they have of finding it.” Sound waves travel farther underwater than on land, he added.
And in the underwater environment, sound also travels further than light, he noted, so “it will be easier to find by listening than by looking.”
